Pentachromacy

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Pentachromacy is the condition of possessing five independent channels for conveying color information. Organisms with pentachromacy are called pentachromats. For these organisms, the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a mixture of no more than five different pure spectral lights.

The normal explanation of pentachromacy is that the organism's retina contains five types of cone cells with different absorption spectra. In practice the number of such receptor types may be greater than five, since different types may be active at different light intensities.

Some birds and butterflies have five or more kinds of colour receptors in their retinae, and are therefore believed to be pentachromats, though psychophysical evidence of functional pentachromacy is not easy to come by. As with tetrachromacy, it is suggested that women carriers of genes for both mild forms of color blindness, deuteranomaly and protanomaly, are born with five different types of color-sensing cones though the red- and green-deficient cones are later lost.